NAME
Spawn::Safe - Fork and exec a process "safely".
EXAMPLE
A basic example:
use Spawn::Safe;
use Data::Dumper;
my $results = spawn_safe({ argv => [ 'ls', '-al', '/var/' ], timeout => 2 });
die Dumper $results;
As a replacement for backticks:
use Spawn::Safe;
# $output = `ls -al /var/`;
$output = spawn_safe(qw{ ls -al /var/ })->{stdout};
SYNOPSIS
Spawn::Safe is a module designed to make "safe" calls to outside
binaries easier and more reliable. Spawn::Safe never invokes a shell
(unless the shell is explicitly requested), so escaping for the shell is
not a concern. An optional timeout is made available, so scripts will
not hang forever, and the caller is able to retrieve both stdout and
stderr. An optional string can be passed to the executed program's
standard input stream.
FUNCTIONS
spawn_safe
Spawn (via fork and exec) the specified binary and capture its output.
Parameters
If passed a single scalar, spawn_safe will assume that to be the the
target binary, and execute it without a limit on runtime.
If passed an array, spawn_safe will execute the first element of the
array as the target binary, with the remaining elements passed as
parameters to the target binary, without a limit on runtime.
The preferred mode is to pass in a single hash reference. When called
this way, the following keys are available:
* argv
Either a string containing the name of the binary which will be
called with no parameters:
my $r = spawn_safe({ argv => 'ls' });
Or an array reference containing the binary and all of its
parameters:
my $r = spawn_safe({ argv => [ 'ls', '-al' ] });
* timeout
The amount of time, in seconds, the binary will be allowed to run
before being killed and a timeout error being returned. If false (or
is otherwise undefined or unset), the timeout will be infinite.
* env
A hash reference containing the new environment for the executed
binary. If false (or otherwise undefined or unset), it will default
to the current environment. You must specify the complete
environment, as the current environment will be overwritten as a
whole. To alter only one variable, a copy of the enviornment must be
made, altered, and then passed in as a whole, eg:
my %new_env = %ENV;
$new_env{'TMP'} = '/var/tmp/';
my $r = spawn_safe({ argv => 'ls', env => \%new_env });
Please note that if a new environment is specified, the new binary's
environment will be altered before the call to exec() (but after the
fork(), so the caller's environment will be unchanged), so the new
environment will take effect before the new binary is launched. This
means that if you alter a part of the environment needed to launch
the binary (eg, by changing PATH, LD_LIBRARY_PATH, etc), these new
variables will need to be set such that the binary can be executed
successfully.
* stdin
A string to be passed to the target binary's standard input stream.
The string will be written into the stream and then the stream will
be closed.
my $r = spawn_safe({ argv => [ '/usr/bin/tr', 'a', 'b' ], stdin => 'aaa' });
Return value
A hash reference will be returned containing one of the following sets
of values:
* If the binary could not be spawned, the single key, 'error' will be
set, which is a text description of the reason the binary could not
be spawned.
* If the binary was executed successfully, but terminated due to a
timeout, the keys 'error', 'stdout', and 'stderr', will be set. The
value for 'error' will be set to 'timed out'. Any data collected
from the executed binary's stdout or stderr will also be made
available, but since the binary was forcefully terminated, the data
may be incomplete.
* If the binary was executed successfully and ran to completion, the
keys 'exit_code', 'stdout, and 'stderr', will all be available.
The key "exit_zero" will always be present, which is true if the binary
is executed successfully and exited with a code of zero.
Notes
The current PATH will be searched for the binary, if available. Open
filehandles are subject to Perl's standard close-on-exec behavior. A
shell will not be invoked unless explicitly defined as the target
binary, as such output redirection and other shell features are
unavailable.
If passed invalid parameters, spawn_safe will croak.
Please note that when specifying a timeout, alarm() is no longer used.
If the clock is stepped significantly backwards during a timeout, a
possibly false timeout error may be thrown. Timeout accuracy should be
within one second.
If a timeout does occur, the spawned program will be sent a SIGKILL
before spawn_safe returns.
COMPATIBILITY
This module attempts to work on MSWin32 but I've been unable to get it
working due to strange issues with IO::Select. I haven't been able to
track down the exact cause, so for now I don't believe this module
functions on MSWin32.
Linux and BSD are tested and supported platforms.
LICENSE
This module is licensed under the same terms as Perl itself.
CHANGES
Version 2.005 - 2013-11-11, jeagle
Add stdin option, clarify docs, add exit_zero return flag.
Version 2.004 - 2012-08-13, jeagle
Include license. Oops.
Version 2.003 - 2012-04-01, jeagle
Untie any tied filehandles before we re-open them to ourselves to work
around any weird tie behavior (should fix issues running under FCGI).
Thanks Charly.
Version 2.002 - 2012-01-04, jeagle
Correct documentation (RT#72831, thanks Stas)
Update unit tests to specify number of tests instead of using no_plan,
otherwse CPAN Testers reports tests fail.
Version 2.001 - 2011-06-13, jeagle
Give the spawned program its own STDIN.
Version 2.000 - 2011-05-12, jeagle
Correct timeout handling. Attempt to correct unit tests for MSWin32, but
there seems to be an issue with IO::Select preventing it from working
properly. Update docs for MSWin32.
Version 1.9 - 2011-05-10, jeagle
Don't use clock_gettime(), use time() and return a timeout if time steps
backwards.
Version 1.8 - 2011-05-09, jeagle
Clean up docs, stop using SIGALARM for timeouts.
Version 1.7 - 2010-07-09, jeagle
Clean up for release to CPAN.
Version 0.4 - 2009-05-13, jeagle
Correct a warning issued when using spawn_safe without a timeout.
Fix compatibility with perl < 5.8.
Version 0.3 - 2009-04-21, jeagle
Clarify documentation regarding use of SIGALRM and for passing of a new
environment.
Correct a warning thrown by exec().
Correct an issue with incorrectly handled timeouts.
Version 0.2 - 2009-04-20, jeagle
Modify API, breaking compatibility, for clarity and expandability.
Add the ability to specify the target program's environment.
Return the (partial) stdout and stderr on a timeout.
Update and clarify documentation.
Version 0.1 - 2009-04-11, jeagle
Inital release.